Format in ISO8601 character format

Arguments

x

An object to convert to ISO8601 character format.

usetz

Include the time zone in the formatting (of outputs including
time; date outputs never include time zone information).

precision

The amount of precision to represent with substrings of
"ymdhms", as "y"ear, "m"onth, "d"ay, "h"our, "m"inute, and "s"econd. (e.g.
"ymdhm" would show precision through minutes. When NULL, full
precision for the object is shown.